"I was advised to," the "Harry's Law" star explains. "I was contracted to go into a movie at that time, 'Little Black Book,' with Brittany Murphy, who I miss very much," she says of the 2004 romantic comedy starring the late Murphy, who died in December 2009 at age 32.

"But my doctors at the time, they had to get insurance approval and all of that, so I was very quiet about it. I had to go back to work right away," Bates adds, explaining that she underwent chemotherapy treatments "by myself ... I guess it's something I felt I had to face on my own."

Continues the "Misery" actress: "Nobody else really knows what you're going through except another cancer patient. Even though your family is supportive and surrounds you."

Although Bates doesn't regret the decision to stay private, she admits, "If I go through it again, I think I would be a lot more open about it." And she applauds Hollywood stars who've shared their cancer battles with the world: "I admire people who have been open like Melissa Ethridge and women I see walking around facing it with out wigs and all of that stuff. I think I would be more courageous next time."